The Peripheral Component Interconnect or PCI Standard defines a computer bus for attaching peripheral devices to a motherboard. The PCI specification describes the physical attributes of the bus, electrical characteristics, bus timing, communication protocols, and more. A PCI Special Interest Group (PCI-SIG) maintains and governs the specifications for various PCI architectures.
In a PCI environment, a host can reset a peripheral device by transmitting a reset command to the device. The reset command is propagated downstream through the PCI hierarchy to reset the device. This procedure works well in environments in which the host does not share the peripheral device with other hosts.
In a shared I/O environment, multiple different hosts share one or more functions of the I/O devices. When a host transmits a reset to a shared I/O device, the reset propagates down the shared PCI link. As a result, the host resets functions of a shared device that it does not own. In other words, the host inadvertently resets functions that are bound to other hosts. This can cause problems since a host could reset functions owned by other hosts.